1. Field of the Invention
The invention relates to a valve for vacuum handling devices or vacuum clamping devices. These are valves that close automatically when a suction point is unoccupied, and thus prevent an undesired leakage from the suction side to the vacuum supply side.
2. Description of the Related Art
Various solutions are known for preventing an undesired leakage when the suction point is unoccupied. By way of example, DE 34 29 444 A1 shows a flow control valve in which a valve body having a spherical design is disposed in a flow channel such that it can be displaced. If the unoccupied suction point draws freely, the sphere is pulled against a seal seat in the flow channel, due to the flow impulse, and closes the flow channel. Because the triggering occurs by means of the flow impulse, valves of this type are prone to malfunction when subjected to flow impacts. Also when the suction point is active, the closed position may be assumed at the start of a suction process, in an undesired manner, due to the initial flow impact.
On the other hand, valves are known with which an automatic closing does not occur due to a flow impulse when the valve draws freely when the suction side is unoccupied, but rather, is initiated by a static pressure difference that is established when the valve draws freely.
DE 198 14 262 C2 shows a valve having a control chamber, delimited by a flexible section of the valve body, that is in constant connection to the vacuum supply side. When the control chamber is compressed, the flexible section is deformed, such that the valve body is brought into its closed position. The control chamber is fully closed off, in terms of flow, with respect to the suction side. When suction occurs while the suction side is unoccupied, no vacuum is created at the suction side. As a result, the control chamber is compressed due to the static pressure difference between the control chamber and suction side, and the valve body is brought into its closed position. With respect to the valves that function by means of flow impulses, this has the advantage that disruptions caused by flow impacts can be avoided. This requires, however, that the time scale for the automatic closing, and the sensitivity to pressure fluctuations must be adjusted to the respective vacuum handling device or vacuum clamping device controlled with the valve.
A vacuum valve is also described in DE 102 16 220 A1, wherein the valve body is formed by a disk-like element.